Sift flour, baking soda, and salt into a medium bowl. Cream butter and sugars with a mixer until pale and fluffy. Beat in ginger, then yolk.
Reduce speed to low, and add flour mixture gradually, beating until just combined. Wrap in plastic, and refrigerate for 1 hour (or up to 2 days).
Preheat oven to 350 degrees. Turn out dough onto lightly floured parchment. Roll out until 1/4 inch thick, and cut out cookies using a 1 3/4-inch heart-shaped cutter. Transfer to parchment-lined baking sheets. Brush each cookie with a damp pastry brush, then sprinkle with sanding sugar. Refrigerate for 15 minutes.
Bake until cookies are set and light gold around edges, 10 to 12 minutes. Let cool on sheets on wire racks for 5 minutes. Transfer cookies to racks, and let cool. Cookies will keep, covered, for up to 3 days.